They really are extremely intelligent birds, also extremely wary with good eye sight. Best way to lure em in is to plant a fake owl on a tall pole, or high in a tree where it can be seen and start calling with a crow call. Crows hate owls and will attack them any chance they get, often calling in their friends to help.
I get crows hanging out in my trees whenever I have a deer, or other game, hanging outside on my game pole when I'm aging the meat. Seems like within hours of hanging a deer they show up. Of course they exit fast when I stick my face outside.
Jeff